Manufacture of fabricated glass articles



Feb. 11, 1936. o. FRlTZE ET AL ,0

MANUFACTURE OF FABRICATED"GLASS ARTICLES Filed Dec. 20, 1954 I INVENTOR5W ma BY AT ORNEY Patented Feb. 11, 1936 UNITED STATES Manor-"Acme orramuca'rnp cuss narrows Otto Fritze, Berlin,

lin-Halensee, Electric Company,

and Alfred Riittenauer, Ber- Germany, assignors to General a corporationof New York Application December 20, 1934, Serial No. 758,514

4 Germany January 3, 1934 2 Claims.

The present invention relates to the manufacture of fabricated glassarticles, such as bulbs or tubes for electric lamps generally and moreparticularly the invention relates to the manufacture of luminescentbulbs or tubes for electric lamps.

Luminescent material can be applied to the inner surface of lamp bulbsor tubes, such as containers for gaseous electric discharge lamps, byapplying a. volatile binding material, such as glycerin or a mixture ofglycerin and boric acid, to the inner surface of the container, dustingluminescent material on the binding material, heating the container tothe vaporizing temperature of the binding material, such as atemperature of 200 to 250 C., and removing the vapor from the container,as by vacuum pumping, for example. A layer or coating of luminescentmaterial remains on the inner surface of the container after the processhas been completed. While the above described process is reasonablysatisfactory for the manufacture of luminescent containers the coatingof luminescent material is rather thin and the fluorescent effectobtained during the operation of the lamp device is not uniform.Further, it is impracticable to heat up a lamp container made by thisprocess to the softening temperature of the glass, for the purpose ofbending the container into a desired configuration or for fusingcontainer parts 'or sections together, for example, since theluminescent material flakes off the container wall at such temperature.

The object of the presentinvention is to provide an improved method andprocess for applying luminescent material to the inner surface of anelectric lamp container. Another object of the invention is to provide aformed container for electric lamps, said container having a smooth,glassy inner surface which is luminescent during the operation of thelamp. A further object of the invention is to provide a luminescentcontainer for an electric lamp device which container is uniformlyluminescent during the operation of the lamp device. A still furtherobject of the invention is toprovide a luminescent container for anelectric lamp device which container is capable of being heated to thesoftening temperature thereof and then bent into desired shape withoutdeleteriously affecting the luminescent qualities thereof. Furtherobjects and advantages of the invention will be apparent from thefollowing detailed description thereof and from the appended claims.

In accordance with these objects the invention comprises the steps ofapplying binding material,

such as glycerin, to the inner surface of a formed lamp container, saidbinding material having a lower volatilizing temperature than thesoftening temperature of the glass of said container, applying particlesof luminescent material on the binding material, raising the pressure inthe container slightly above barometric pressure and then heating thecontainer to the softening temperature of the glass thereof. Whendesired, the increase in pressure and the heating of the container takesplace simultaneously. The heating of the container to the softeningtemperature thereof is beneficial since the binding material iscompletely vaporized, no residue thereof being left on the container,and the luminescent material adheres better to the wall of the containersince the particles of luminescent material sink into the softened wallof the container andare completely or partially embedded therein to forma homogeneous body. The luminescent particles are fused to saidcontainer wall as well as to each other and after the heating the innersurface of the container is smooth and glassy whereas when the containeris heated only to the volatilizing temperature of the binding material,as in the process first described, the inner surface of the container isrough and granular. The slightly elevated pressure in the containermaintains the container in the original shape thereof during the heatingperiod. It will be understood, of course, that the softening temperatureof the container glass is below that temperature at which deleteriouschemical changes in the luminescent material take place.

The strong adhesion between the luminescent material and the inner wallof the container characteristic of lamp containers manufactured inaccordance with the process of the present invention has manyadvantages. Tubular containers are heated and then bent into desiredshapes and tube sections or parts are spliced or fused together withoutthe luminescent material flaking off. Further, a large quantity ofluminescent material is embedded in the container so that uniformfluorescence is obtained over the container during the operation of thelamp and when the lamp isnot operating the container has the appearanceof a good opal glass container.

We have demonstrated that a matte inner surface on the container isadvantageous. The binding material adheres better to such a surface anddoes not run of! spots on the inner surface. Thus the luminescentmaterial subsequently ap- Thuringer glass of commerce, such as a sodaglass, is heated to a temperature of 550 to 600 C. during the process.The pressure in the container during the heating thereof depends uponthe dimensions of the container, particularly the thickness ofthe wallsthereof. Generally a pressure of approximately 0.2 to 0.5 atmospheresover barometric pressure is sufficient to maintain the container in itsoriginal shape during the heating period. Such pressures are produced byconnecting the container through the exhaust tube thereof to an airpressure line, when desired, or when desired, air under barometricpressure is introduced into the container which is then sealed. In thislatter case the heating of the sealed container automatically increasesthe gas pressure therein sufficiently toprevent the container fromcollapsing when heated to the softening temperature of the glassthereof. In either case the vapor of the binding agent is removed, byvacuum pumping, for example, after the temperature of the container hasdropped below the temperature at which the container glass is plastic.When desired, the container glass is ultra violet transmitting in whichcase the luminescent particles whether completely or partly embedded inthe container are light emitting during the operation of the lamp deviceand substantially all the ultra v violet light emitted by the dischargein the lamp is transformed into visible light by said lumines centmaterial.

Any of the well known visible light transmitting luminescent materials,such as zinc sulfide, zinc silicate, cadmium tungstate, zinc cadmiumsulfide, zinc borate, cadmium bcrate, calcium tungstate or magnesiummolybdate are used in the process, when desired. The new and novelprocess is applicable to the containers of lamp devices having visibleand ultra violet light emitting, current carrying solid bodies, such asincandescent lamps, as well as containers of gaseous electric dischargelamps.

In the drawing accompanying and forming part of this specification twogaseous, electric discharge vapor lamps each having a luminescentcontainer made in accordance with the present invention are shown, inwhich Fig, 1 is a side elevational, partly sectional view of one gaseouselectric discharge lamp, and

Fig. 2 is an enlarged sectional view of the part of the lamp containershown in section in Fig. 1,

Fig. 3 is a side elevational, partly sectional view of another gaseouselectric discharge lamp, and

Fig. 4 is an enlarged sectional view of the part of the lamp containershown in section in Fig. 3.

Referring to Figures 1 and 3 of the drawing the gaseous electricdischarge lamp device comprises a tubular container I having a pair ofthermionic electrodes 2 and 3 sealed into the ends thereof. Saidcontainer I has a rare, starting gas therein such as argon and aquantity 5 of vaporizable material, such as mercury. During theoperation of the device the electrically excited mercury vapor emitsvisible and ultra violet light. The inner surface of said container l ofthe lamp devices illustrated in Figs. 1 and 2 has embedded therein alight transmitting, luminescent material 4, such as zinc silicate, whichmaterial is applied to said container I by the above described process.The luminescent material 4 (indicated by dots in the drawing) is showncompletely embedded in said inner surface in Figs. 1 and 2 partlyembedded in said inner surface in Figs. 3 and 4. During the operation ofthe lamp device the ultra violet rays striking the luminescent materialare transformed thereby into visible light rays which complement thespectrum of the visible light emitted by the electrically excitedgaseous atmosphere during the operation of the lamp device andsupplement the intensity of the light emitted by said gaseousatmosphere.

While we have illustrated and described a particular form of lamp deviceit will be understood, of course, that the invention is applicable tolamp devices having different structures, for example, the invention isuseful in connection with lamp devices of the type wherein the containerhas a single stem at one end thereof and in connection with lamp deviceshaving a vaporizable electrode, of mercury for example, such as the wellknown Cooper Hewitt mercury vapor lamp of commerce.

What we claim as new and desire to secure by Letters Patent of theUnited States is:--

1. A process for applying luminescent material to the inner surface ofthe container of an electric lamp device which comprises the steps ofapplying a binding material having a lower volatilizing temperature thanthe softening temperature of said container to said inner surface,applying luminescent material to the binding material, increasing thepressure in said container slightly above barometric pressure andheating the container to the softening temperature thereof to remove thebinding material and to cause the said luminescent material to be fusedinto the container and to present a smooth glassy surface thereat.

2. A process for applying luminescent material to the inner surface ofthe container of a gaseous electric discharge lamp device whichcomprises the steps of applying a binding material having a lowervolatilizing temperature than the softening temperature of saidcontainer to said inner surface, applying luminescent material to thebinding material, increasing the pressure in said container slightlyabove barometric pressure by connecting said container to a source ofgas under a pressure slightly greater than barometric pressure andheating the container to the softening temperature thereof to remove thebinding material and to cause the said luminescent material to be fused.into the container and to present a smooth glassy surface thereat.

o'rro FRITZE. ALFRED RiiT'rENAUER.

